Thermal trip assembly and circuit interrupter including the same

Abstract

A thermal trip assembly for use with a busbar includes a fastener, an insulating sleeve, a temperature sensor structured to sense a temperature of the busbar, and a thermal trip circuit structured to output a trip signal based on the sensed temperature. A portion of the insulating sleeve is disposed between the temperature sensor and the busbar. The fastener couples the insulating sleeve and the temperature sensor to the busbar with the insulating sleeve being in direct contact with a portion of the busbar.

What is claimed is: 
     
       1. A thermal trip assembly for use with a busbar, the thermal trip assembly comprising:
 a fastener including a first prong, a second prong, and a central member, wherein the central member is connected to the first prong and the second prong; 
 an insulating sleeve; 
 a temperature sensor structured to sense a temperature of the busbar; and 
 a thermal trip circuit structured to output a trip signal based on the sensed temperature, 
 wherein the fastener is structured to couple the thermal trip assembly to the busbar such that the insulating sleeve, the temperature sensor, and the busbar are disposed between the first prong and the second prong when the thermal trip assembly is coupled to the busbar, 
 wherein a portion of said insulating sleeve is disposed between the temperature sensor and the busbar when the thermal trip assembly is coupled to the busbar; and 
 wherein the insulating sleeve is in direct contact with a portion of the busbar when the thermal trip assembly is coupled to the busbar. 
 
     
     
       2. The thermal trip assembly of  claim 1 , wherein the insulating sleeve is composed of thermal silicone material. 
     
     
       3. The thermal trip assembly of  claim 1 , wherein the insulating sleeve has a thermal conductivity within a range of about 1.2 W/mK to about 1.8 W/mK; and wherein the insulating sleeve has a specific heat capacity within a range of about 1.05 kJ/kgK to about 1.3 kJ/kgK. 
     
     
       4. The thermal trip assembly of  claim 1 , wherein the temperature sensor is a thermal diode. 
     
     
       5. The thermal trip assembly of  claim 1 , wherein the thermal trip assembly further includes an ambient temperature sensor disposed apart from the busbar and structured to sense an ambient temperature; and wherein the thermal trip circuit is structured to output the trip signal based on the sensed temperature of the busbar and the sensed ambient temperature. 
     
     
       6. The thermal trip assembly of  claim 5 , wherein the ambient temperature sensor is a thermal diode. 
     
     
       7. The thermal trip assembly of  claim 5 , wherein the thermal trip circuit includes:
 a temperature sensing circuit structured to output a voltage based on the temperature sensed by the temperature sensor; 
 a differential amplifier circuit structured to amplify to an output a difference between the voltage output by the temperature sensing circuit and a first predetermined voltage; 
 a follower circuit structured to buffer to an output a voltage of the output of the differential amplifier circuit; 
 an integrator circuit structured to smooth to an output a voltage of the output of the follower circuit; 
 an ambient temperature sensing circuit structured to output a voltage based on the ambient temperature sensed by the ambient temperature sensor; 
 an ambient differential amplifier circuit structured to amplify to an output a difference between the voltage output by the ambient temperature sensing circuit and a second predetermined voltage; 
 an ambient follower circuit structured to buffer to an output a voltage of the output of the ambient differential amplifier circuit; 
 an ambient integrator circuit structured to smooth to an output a voltage of the output of the ambient follower circuit; 
 an ambient output circuit structured to buffer to an output a voltage of the output of the ambient integrator circuit; and 
 a comparator circuit structured to combine a voltage of the outputs of the integrator circuit and the ambient output circuit, to compare a voltage of the combined outputs of the integrator circuit and the ambient output circuit with a third predetermined voltage, and to output the trip signal when the combined outputs of the integrator circuit and the ambient output circuit are greater than the third predetermined voltage. 
 
     
     
       8. The thermal trip assembly of  claim 1 , wherein the fastener is a metallic clip. 
     
     
       9. The thermal trip assembly of  claim 1 , wherein the busbar includes a flat portion; and wherein the insulating sleeve is structured to be in direct contact with the flat portion of the busbar. 
     
     
       10. A thermal trip assembly for use with a busbar, the thermal trip assembly comprising:
 a fastener; 
 an insulating sleeve; 
 a temperature sensor structured to sense a temperature of the busbar; and 
 a thermal trip circuit structured to output a trip signal based on the sensed temperature, 
 wherein a portion of said insulating sleeve is disposed between the temperature sensor and the busbar; and 
 wherein the fastener couples the insulating sleeve and the temperature sensor to the busbar with the insulating sleeve being in direct contact with a portion of the busbar; and 
 wherein the thermal trip circuit includes: 
 a temperature sensing circuit structured to output a voltage based on the temperature sensed by the temperature sensor; 
 a differential amplifier circuit structured to amplify to an output a difference between the voltage output by the temperature sensing circuit and a first predetermined voltage; 
 a follower circuit structured to buffer to an output a voltage of the output of the differential amplifier circuit; 
 an integrator circuit structured to smooth to an output a voltage of the output of the follower circuit; and 
 a comparator circuit structured to compare a voltage of the output of the integrator circuit with a second predetermined voltage and to output the trip signal when the output of the integrator circuit is greater than the second predetermined voltage. 
 
     
     
       11. A circuit interrupter comprising:
 a first terminal; 
 a second terminal; 
 a plurality of busbars electrically connecting the first and second terminals; 
 separable contacts moveable between a closed position and an open position, the first and second terminals being electrically disconnected from each other when the separable contacts are in the open position; 
 an operating mechanism structured to open said separable contacts; 
 an actuator structured to cooperate with said operating mechanism to trip open said separable contacts; 
 a current sensor structured to sense a current flowing between the first and second terminals; 
 a current transformer structured to harvest power from the current flowing between the first and second terminals; and 
 an electronic trip unit including:
 an other trip function circuit structured to output a first trip signal to control the actuator to cooperate with the operating mechanism to trip open the separable contacts based on the current sensed by the current sensor; and 
 a thermal trip assembly comprising:
 a fastener including a first prong, a second prong, and a central member, wherein the central member is connected to the first prong and the second prone; 
 an insulating sleeve; 
 a temperature sensor structured to sense a temperature of one of the plurality of busbars; and 
 a thermal trip circuit structured to output a second trip signal based on the sensed temperature, 
 
 
 wherein the fastener is structured to couple the thermal trip assembly to the said one of the plurality of busbars such that the insulating sleeve, the temperature sensor, and said one of the plurality of busbars are disposed between the first prong and the second prong when the thermal trip assembly is coupled to said one of the plurality of busbars; 
 wherein a portion of said insulating sleeve is disposed between the temperature sensor and said one of the plurality of busbars when the thermal trip assembly is coupled to said one of the plurality of busbars; and 
 wherein the insulating sleeve is in direct contact with a portion of said one of the plurality of busbars when the thermal trip assembly is coupled to said one of the plurality of busbars. 
 
     
     
       12. The circuit interrupter of  claim 11 , wherein the insulating sleeve is composed of thermal silicone material. 
     
     
       13. The circuit interrupter of  claim 11 , wherein the insulating sleeve has a thermal conductivity within a range of about 1.2 W/mK to about 1.8 W/mK; and wherein the insulating sleeve has a specific heat capacity within a range of about 1.05 kJ/kgK to about 1.3 kJ/kgK. 
     
     
       14. The circuit interrupter of  claim 11 , wherein the temperature sensor is a thermal diode. 
     
     
       15. The circuit interrupter of  claim 11 , wherein the thermal trip assembly further includes an ambient temperature sensor disposed apart from the plurality of busbars and structured to sense an ambient temperature; and wherein the thermal trip circuit is structured to output the second trip signal based on the sensed temperature of the one of the plurality of busbars and the sensed ambient temperature. 
     
     
       16. The circuit interrupter of  claim 15 , wherein the ambient temperature sensor is a thermal diode. 
     
     
       17. The circuit interrupter of  claim 15 , wherein the thermal trip circuit includes:
 a temperature sensing circuit structured to output a voltage based on the temperature sensed by the temperature sensor; 
 a differential amplifier circuit structured to amplify to an output a difference between the voltage output by the temperature sensing circuit and a first predetermined voltage; 
 a follower circuit structured to buffer to an output a voltage of the output of the differential amplifier circuit; 
 an integrator circuit structured to smooth to an output a voltage of the output of the follower circuit; 
 an ambient temperature sensing circuit structured to output a voltage based on the ambient temperature sensed by the ambient temperature sensor; 
 an ambient differential amplifier circuit structured to amplify to an output a difference between the voltage output by the ambient temperature sensing circuit and a second predetermined voltage; 
 an ambient follower circuit structured to buffer to an output a voltage of the output of the ambient differential amplifier circuit; 
 an ambient integrator circuit structured to smooth to an output a voltage of the output of the ambient follower circuit; 
 an ambient output circuit structured to buffer to an output a voltage of the output of the ambient integrator circuit; and 
 a comparator circuit structured to combine a voltage of the outputs of the integrator circuit and the ambient output circuit, to compare a voltage of the combined outputs of the integrator circuit and the ambient output circuit with a third predetermined voltage, and to output the second trip signal when the combined outputs of the integrator circuit and the ambient output circuit are greater than the third predetermined voltage. 
 
     
     
       18. The circuit interrupter of  claim 11 , wherein the fastener is a metallic clip. 
     
     
       19. The circuit interrupter of  claim 11 , wherein said one of the plurality of busbars includes a flat portion; and wherein the insulating sleeve is structured to be in direct contact with the flat portion of said one of the plurality of busbars. 
     
     
       20. The circuit interrupter of  claim 11 , wherein the current transformer provides the harvested power to the thermal trip assembly. 
     
     
       21. The circuit interrupter of  claim 11 , wherein the electronic trip unit outputs the first trip signal to initiate an instantaneous trip and the thermal trip assembly outputs the second trip signal to initiate a temperature based trip. 
     
     
       22. A circuit interrupter comprising:
 a first terminal; 
 a second terminal; 
 a plurality of busbars electrically connecting the first and second terminals; 
 separable contacts moveable between a closed position and an open position, the first and second terminals being electrically disconnected from each other when the separable contacts are in the open position; 
 an operating mechanism structured to open said separable contacts; 
 an actuator structured to cooperate with said operating mechanism to trip open said separable contacts; 
 a current sensor structured to sense a current flowing between the first and second terminals; 
 a current transformer structured to harvest power from the current flowing between the first and second terminals; and 
 an electronic trip unit including:
 an other trip function circuit structured to output a first trip signal to control the actuator to cooperate with the operating mechanism to trip open the separable contacts based on the current sensed by the current sensor; and 
 a thermal trip assembly comprising:
 a fastener; 
 an insulating sleeve; 
 a temperature sensor structured to sense a temperature of one of the plurality of busbars; and 
 a thermal trip circuit structured to output a second trip signal based on the sensed temperature, 
 
 
 wherein a portion of said insulating sleeve is disposed between the temperature sensor and said one of the plurality of busbars; and 
 wherein the fastener couples the insulating sleeve and the temperature sensor to said one of the plurality of busbars with the insulating sleeve being in direct contact with a portion of the one of the plurality of busbars; 
 wherein the thermal trip circuit includes: 
 a temperature sensing circuit structured to output a voltage based on the temperature sensed by the temperature sensor; 
 a differential amplifier circuit structured to amplify to an output a difference between the voltage output by the temperature sensing circuit and a first predetermined voltage; 
 a follower circuit structured to buffer to an output a voltage of the output of the differential amplifier circuit; 
 an integrator circuit structured to smooth to an output a voltage of the output of the follower circuit; and 
 a comparator circuit structured to compare a voltage of the output of the integrator circuit with a second predetermined voltage and to output the second trip signal when the output of the integrator circuit is greater than the second predetermined voltage.